1. Field of the Application
The present invention relates to ferrous and non-ferrous metallurgy and, more particularly, to the practice of semicontinuous casting of metal.
This present invention will find application in casting large-size sections which undergo further forging and rolling operations, as well as for manufacturing consumable electrodes for use in electroslag remelting and vacuum arc melting processes.
To meet an ever growing demand of metallurgical and machine-building industries in large-size cast sections, the production of the large size cast sections should be drastically increased. The castings of this type are required in great number for blooming and slabbing mills, as well as in forgery shops. When cast in iron moulds, the ingots for roughing mills are cut off with the resultant 11 to 16 percent of metal being lost in the zone of shrinkage cavity.
Large-size ingots (400 to 1300 mm in cross-sectional diameter) are needed for use in electroslag remelting and vacuum arc melting processes. These modern processes for the production of metal workpieces open the way for improvement of metal quality. Therefore, it is of particular importance that the electroslag and vacuum arc melting installations should be provided with consumable electrodes of large cross section.
2. Description of the Prior Art
A number of installations have been recently built to carry out semicontinuous casting of consumable electrodes. It has been found in the course of their operation that the gain in yield was up from 6 to 9 percent, and the quality of ingots produced by either electroslag or vacuum arc melting process was improved. In modern practice of casting large-size consumable electrodes, use is made of elongated build-up iron moulds. However, due to the splashing of molten metal poured from a height of 6 to 8 meters, the surface quality of consumable electrodes is impaired and the amount of metal lost during pouring is increased. It is therefore obvious that this process of casting consumable electrodes needs drastic improvement.
It should also be observed that the bottom casting of metal in elongated iron moulds is ineffective, since the metal undergoes undercooling in the meniscus area, thereby causing metal defects or flaws.
The now-in-use technological process for casting large-size ingots to be worked in forging shops is likewise far from being perfect. During this process the ingots are cast in iron moulds. The gain in yield amounts to only 65 to 70 percent. Needless to say that the casing process during which there is wasted from 30 to 35 percent of the metal is quiet unsatisfactory.
As to continuous-casting machines, these are suitable only for the production of ingots having cross-sectional dimensions of up to 400.times.400 mm. Any further increase in the cross-sectional size of ingots necessitates casting machines of appreciably larger working heights, which, in turn, renders them more complicated in construction and increases capital cost for their installation.
Therefore, attempts have been taken to develop a machine for semicontinuous casting of metal, suitable for the production of large-size ingots.
For example, there is known a semicontinuous-casting machine disclosed in USSR Inventor's Certificate No. 325,088, which comprises a mould and a dummy bar positioned on a platform movable along guides with the aid of a rope drive mechanism intended to effect the casting withdrawal operation.
However, the machine of the Inventor's Certificate referred to above is very large in height, which is because of the fact that the pulley system is provided in the mould area . In addition, by reason of insufficient rigidity of the casting withdrawal mechanism, the casting of large mass is not moved smoothly but in jerks. This, in turn, adversely affects the casting quality, results in nonheterogenous properties of the casting metal, causes crackings and other flaws to appear in the casting, and causes excessive dynamic loads acting on the casting machine as a whole.
The disposition of the pulley system and rope in the zone of elevated temperatures reduces their service life and impairs operating reliability of the semicontinuous-casting machine.
There is also known a semicontinuous-casting machine described in the book "Continuous Casting of Steel" by M. C. Boichenko et al., USSR, Moscow, Metallurgizdat Publishers, 1961, p. 31, which comprises a mould and a dummy bar positioned on a movable platform sliding along guides with the aid of the casting withdrawal screw drive mechanism.
The casting machine mentioned above also has a considerable working height, which is dictated by the necessity to arrange the casting withdrawal drive mechanism below the mould (the drive being in top position), or below the movable platform (the drive being in bottom position).
Difficulties also arise when it comes to the production of long-size castings, requiring the provision of rather lengthy screws for the casting withdrawal mechanism, which are manufactured in a limited number. Furthermore, the arrangement of the screws of the casting withdrawal drive mechanism in close proximity to the casting, i.e. in the zone of elevated temperatures, increases the rate of wear of these screws, reduces their service life and impairs operating reliability of the casting machine as a whole.
USSR Inventor's Certificate No. 537,751 describes a machine for semicontinuous casting of metal, which comprises a mould and a dummy bar positioned on a movable platform sliding along guides with the aid of the rack-and-gear drive casting withdrawal mechanism. The casting withdrawal mechanism includes stationary mounted racks and gear wheels arranged on a movable platform and driven from an electro-mechanical actuator also positioned on the movable platform.
The casting machine of the Inventor's Certificate referred to above also suffers from a number of serious disadvantages, namely: it is complicated in construction, the platform-mounted casting withdrawal drive mechanism being cumbersome; the bulky structure of the casting withdrawal drive mechanism restricts the production of massive castings; and the height of the casting machine is enormous, which is due to the location of the casting withdrawal drive mechanism on the movable platform.
There is also known another semicontinuous-casting machine described in the book "Continuous Casting" by Erhard Germann, USSR, Metallurgizdat Publishers, Moscow, 1961, p. 419, FIG. 1290, which comprises a mould arranged above a secondary-cooling chamber and a dummy bar made up of a lower fixed section and an upper movable section. The lower fixed section of the dummy bar is made in the form of hydraulic cylinder with the piston rod thereof interacting with the upper section of the dummy bar.
The casting machine in question is simple in construction and has sufficient rigidity permitting the production of massive castings of large cross section.
However, this casting machine suffers from a disadvantage, it being its considerable working height which includes the length of the mould, the length of the casting and the length of the lower fixed section of the dummy bar, i.e. the length of the hydraulic cylinder body which is larger in length than the casting, since the cylinder functions, on the one hand, to introduce the upper section of the dummy bar into the mould cavity and, on the other hand, to ensure the formation of the casting of a prescribed length, as well as its complete withdrawal from the mould. It should be observed that the dummy bar upper section is moved from the uppermost position to the lowermost position in one piston stroke of the hydraulic cylinder.
The enormous height of the casting machine renders its installation difficult in modern shops of metallurgical and machine-building plants. If its installation is effected in newly built shops, the height of the shops should be considerably increased, thus resulting in a higher capital cost for the installation of both the shop and the casting machine.